Visual liquid level indicator

ABSTRACT

A tank and liquid level indicator has first housing that holds a liquid and a second elongated housing in fluid communication with the first elongated housing so that a liquid level in the second housing is approximately equal to the level in the first housing. A float in the second housing cooperates with the circuitry to operate one or more light switches. A light-transmissive cover is disposed over the light source.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. provisional patentapplication Ser. No. 62/256,925, filed Nov. 18, 2015, entitled VISUALLIQUID LEVEL INDICATOR, the entire disclosure of which is herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to level indicators and, moreparticularly, to an indicator for a level of fluid in a storage tank orvessel.

BACKGROUND OF THE INVENTION

Easy to view liquid level indication devices that are both accurate andnearly indestructible are known in the art. For example, liquid levelindicators sold under the name SURESITE by GEMS Sensors, Inc. ofPlainville, Conn. are available for use in applications where quickvisual communication of tank contents is required. Such indicatorsoperate without power in temperatures to 750° F. (399° C.) and inpressures up to 4200 psi (290 bar) and are unaffected by extreme thermalchanges. In addition, sight glasses are available, although such devicesare relatively more fragile and breakable.

Thus, SURESITE liquid level indicators are a durable and saferalternative to sight glasses. Each SURESITE indicator includes an alloy,stainless steel alloy, or engineered plastic housing and mountsexternally to a top or side of a liquid storage tank to provideeasy-to-read, continuous level gauging. A magnetic level indicator isisolated from the measured media in a pressure-tight housing, allowingthe SURESITE indicator to be used in areas where the use of sightglasses may not be possible. The magnetic level indicator comprises aseries of vertically-spaced flags each having first sides with a firstcolor and second sides with a contrasting second color. A magnetic floattraveling within a housing adjacent to the indicator sequentially flipseach flag, thereby showing a series of flags with the first color facingoutward a second series of flags with the second color facing outward,thereby indicating that the liquid level is approximately between thefirst and second series of flags. U.S. Pat. No. 4,512,190 discloses anearly fluid level indicator of a similar embodiment. SURESITE indicatorsare unaffected by tank shape, condensation, atmospheres, foam,stratification of vapors, high temperatures, or flux and do not requirecontinual calibration. Modular accessories, such as switches, scales,and continuous transmitters, increase capabilities.

However, known visual liquid level indicators are difficult to use indark, tight, confined, or hard to reach locations. For example, knownindicators provide far less utility when used in radiator cabinets,engine rooms, or open areas, such as oil storage tank fields, breweries,and dairy farms that use several tanks.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

SUMMARY OF THE INVENTION

The present invention recognizes and addresses considerations of priorart constructions and methods.

In one embodiment, a tank and liquid level indicator includes a firsthousing enclosing a first volume that holds a liquid and a secondelongated housing enclosing a second volume, wherein the second housingis attached to an exterior of the first housing so that the secondvolume is in fluid communication with the first volume so that a levelof the liquid within the second volume is approximately equal to a levelof the liquid in the first volume. A float is disposed within the secondvolume and is buoyant with respect to the liquid so that the float moveswith the level of the liquid in the second volume along a first axispassing through a center of the float. At least a portion of the floatis magnetic so that a magnetic field extends from the float. A pluralityof magnetic sensors are aligned sequentially with respect to each otherin a direction having a vertical component. The magnetic sensors aredisposed with respect to the second volume so that movement of the floatwithin the second volume in response to the level of the liquid withinthe second volume causes sequential detection of the magnetic field byrespective magnetic sensors of the plurality of sensors. At least onelight source is in electrical communication with the plurality ofmagnetic sensors so that the magnetic sensors control actuation of theat least one light source in response to the detection of the magneticfield. A light-transmissive cover is attached to the second housing sothat the at least one light source is disposed between the secondhousing and an outer surface of the light-transmissive cover. The outersurface is disposed on at least one side of a first plane that isparallel to the first axis and at an outer surface of the second housingand is disposed on an opposite side of the first axis from the firsthousing. The at least one light source is disposed with respect to theouter surface of the cover so that a first portion of light from the atleast one light source passes through the first plane and a secondportion of the light from the light source travels away from the plane.

In another embodiment, a tank and liquid level indicator has a firsthousing enclosing a first volume that holds a liquid. A second generallycylindrical housing has annular cross-sections and encloses a secondvolume. The second housing is attached to an exterior of the firsthousing so that the second volume is in fluid communication with thefirst volume so that a level of the liquid within the second volume isapproximately equal to a level of the liquid in the first volume. Agenerally cylindrical float is disposed within the second volume and isbuoyant with respect to the liquid so that the float moves with thelevel of the liquid in the second volume along a first axis passingthrough a center of the float. At least a portion of the float ismagnetic so that a magnetic field extends from the float. A plurality ofmagnetic sensors is aligned sequentially with respect to each other in adirection having a vertical component. The magnetic sensors are disposedwith respect to the second volume so that movement of the float withinthe second volume in response to the level of the liquid within thesecond volume causes sequential detection of the magnetic field byrespective said magnetic sensors of the plurality of sensors. At leastone light source is in electrical communication with the plurality ofmagnetic sensors so that the magnetic sensors control actuation of theat least one light source in response to the detection of the magneticfield. A light-transmissive cover is attached to the second housing sothat the at least one light source is disposed between the secondhousing and an outer surface of the light-transmissive cover. The outersurface extends across and beyond both sides of a first plane that isparallel to the axis and tangential to an outer surface of the secondhousing, and the at least one light source is disposed on an oppositeside of the first axis from the first housing. The at least one lightsource is disposed with respect to the outer surface of the cover sothat light from the at least one light source passes through the firstplane and away from the first plane.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more embodiments of theinvention and, together with the description, serve to explain one ormore embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendeddrawings, in which:

FIG. 1 is a schematic view of a tank and liquid level indicator inaccordance with an embodiment of the present invention;

FIG. 2 is a plan view of the liquid level indicator of FIG. 1;

FIG. 3 is a schematic view of a float for use in the liquid levelindicator of FIG. 1;

FIG. 4 is a partial top view of the liquid level indicator of FIG. 1;

FIG. 5 is a partial view of an arrangement of reed switches for use inthe liquid level indicator of FIG. 1;

FIG. 6 is a diagram of an electrical circuit for use in the liquid levelindicator of FIG. 1;

FIG. 7 is a top partial perspective view of the tank and liquid levelindicator of FIG. 1 with reference geometry; and

FIG. 8 is a partial view a magnet-holding portion of the float for usein the liquid level indicator of FIG. 1.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention according to the disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to presently preferred embodimentsof the invention, one or more examples of which are illustrated in theaccompanying drawings. Each example is provided by way of explanation,not limitation, of the invention. In fact, it will be apparent to thoseskilled in the art that modifications and variations can be made in thepresent invention without departing from the scope and spirit thereof.For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

As used herein, terms referring to a direction or a position relative tothe orientation of the level indicator, such as but not limited to“vertical,” “horizontal,” “upper,” “lower,” “above,” or “below,” referto directions and relative positions with respect to the levelindicator's orientation in its normal intended operation, as indicatedin FIG. 1 herein. Thus, for instance, the terms “vertical” and “upper”refer to the vertical direction and relative upper position in theperspectives of FIG. 1 and should be understood in that context, evenwith respect to a liquid level indicator that may be disposed in adifferent orientation.

Further, the term “or” as used in this disclosure and the appendedclaims is intended to mean an inclusive “or” rather than an exclusive“or.” That is, unless specified otherwise, or clear from the context,the phrase “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, the phrase “X employs A or B” issatisfied by any of the following instances: X employs A; X employs B;or X employs both A and B. In addition, the articles “a” and “an” asused in this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or clear fromthe context to be directed to a singular form. Throughout thespecification and claims, the following terms take at least the meaningsexplicitly associated herein, unless the context dictates otherwise. Themeanings identified below do not necessarily limit the terms, but merelyprovided illustrative examples for the terms. The meaning of “a,” “an,”and “the” may include plural references, and the meaning of “in” mayinclude “in” and “on.” The phrase “in one embodiment,” as used hereindoes not necessarily refer to the same embodiment, although it may.

Referring now to FIG. 1, a tank 10 has an inlet 12 and outlet 13 forproviding a liquid 20 with an ingress and an egress, respectively, to aninterior volume 11 of tank, or housing, 10. Tank 10 may be made of asuitable material, such as a stainless steel, a unitary polymer, alayered polymer composite, a reinforced composite polymer, or a suitablemetal. Tank 10 fluidly couples with a nonmagnetic elongated housing 50extending vertically along tank 10 that is in fluid communication withinterior volume 11 of tank 10 via an upper conduit 51 and a lowerconduit 52 so that a liquid level 14 within tank 10 is approximatelyequal to a liquid level 54 within the housing. Conduits 51, 52 couplewith tank 10 through process ports via adapters such as, for example,nipples or flanges. For example, a tank having a pair of process portswith flanges may couple with housing 50 via matching flanges that attachvia bolts to the tank's flanges.

Referring to FIG. 2, elongated housing 50 has a hollow generallycylindrical profile and is fabricated in part from a tube having its topend capped and welded shut. Housing 50 has a bottom flange 55 that mateswith a sealing plate 56 via nuts and bolts, or collectively, fasteners57. A gasket is placed between flange 55 and plate 56 to seal housing 50from leaks. By removing sealing plate 56, an access to housing 50 isexposed through which a float 80 (FIG. 1) is inserted into the interiorof housing 50. Conduits 51, 52 (FIG. 1) are welded to a side of housing50 at openings to housing 50's interior. Thus, the only inlets andoutlets of housing 50 are conduits 51 and 52.

Float 80, illustrated in FIGS. 1 and 3, travels within an interior ofhousing 50 and has a dimension in housing 50's elongation direction thatis greater than a major dimension of housing 50's cross sectionperpendicular to the elongation direction so that float 80 is held witha consistent vertical orientation and cannot rotate (other than a slightamount allowed by the tolerance between the float and the interior wallof housing 50 that allows relative movement between the two components)around an axis that is perpendicular to the elongation direction ofhousing 50. That is, a top of float 80 is fixed as the top and cannotrotate within housing 50 to become a bottom of float 80. In theillustrated embodiment, float 80 is generally cylindrical, having aheight that is greater than housing 50's inner diameter. Moreover, float80 fits within the interior of housing 50 with an outer diameter that isslightly less than housing 50's inner diameter so as to minimizerotation around an axis perpendicular to housing 50's elongationdirection. Float 80 has an average density that is greater than the airin the tank but less than the liquid in the tank. In this way, float 80is buoyant with respect to liquid 20 (FIG. 1) and will extend arelatively fixed amount below liquid level 14 (FIG. 1).

Referring now to FIG. 3, float 80 has an approximately cylindricalprofile, having annular cross-sections and filleted upper and loweredges. Float 80 comprises a drawn nonmagnetic stainless steel cup-shapedbottom portion 81 and a drawn nonmagnetic stainless cup-shaped topportion 82. Top portion 82 is swaged to form a shoulder fabricated nearits bottom edge having a larger inner diameter than bottom portion 81'souter diameter so that bottom portion 81 fits partially within topportion 82 to the depth of the shoulder.

Referring also to FIG. 8, a magnet-holding inner portion 83 has acylindrical and hollow elongated portion along the axis of float 80(i.e. the vertical direction in FIG. 3) with a series of U-shaped slotscut or otherwise formed in the cylindrical side wall to form tabs 84spaced vertically in pairs across opposite sides of the float (e.g.,some of the tabs are on the left, and some are on the right, of thecylindrical portion in FIG. 8). Magnet-holding portion 83 has an openingon a bottom flanged side and is therefore configured to receive acylindrical magnet 88 (having a diameter that is slightly less than theinner diameter of magnet portion 83 to enable insertion but limitmovement in radial directions from the axis of magnetic portion 83).Once magnet 88 is inserted, opposing tabs 84 above and opposing tabs 84below magnet 88 are bent inwards (a pair bending downwards and a pairbending upwards to fold against a top and a bottom of the magnet,respectively, so that two tabs fold against the top and two tabs foldagainst the bottom of the magnet) to hold magnet 88 in place along innerportion 83's axial direction. In this way, the magnet is inserted (withits north-south axis in the vertical direction of FIG. 3) into itslocation and held by bent tabs 84 in a fixed position with respect tothe bottom of the float, the position determined based on the specificgravity of the liquid held in the tank so that the height of the magnet,when float 80 is floating on liquid 20, is at the same level as theliquid. Thus, by selecting a slot at a height above the bottom of float80 that is equal to the depth into which float 80 extends into liquid20, when float 80 is floating on liquid 20, the magnet is disposed atthe level of liquid 20. For example, the lower the density of liquid 20,the lower float 80 will extend down into the liquid, so that a lowerdensity liquid requires selection of a magnet slot higher up on float 80than for a higher density liquid in order for the magnet to be held atthe liquid level. In this way, float 80 is calibrated for the density ofthe particular liquid within tank 10. Inner portion 83 comprises awasher 85 or flanged portion that has approximately the same outerdiameter as the outer diameter of bottom portion 81 so that washer 85rests on top of bottom portion 81 and fits within the shoulder of topportion 82. Top portion 82 is placed over an outer radial edge of washer85 and partially over bottom portion 81, and is then fusion-welded,creating a seal between bottom portion 81 and top portion 82, therebytrapping air within an interior of float 80. In this way, the averagedensity of the air-filled stainless steel unit is less than a netdensity of its components.

Referring to FIG. 4, a visual indicator 100 clips to housing 50 (FIG. 1)as further discussed below. Visual indicator 100 comprises a shroud 105comprising a light-transmissive (i.e. transparent or translucent)polymer, such as for example, polycarbonate, and has an elongatedprofile with consistent cross sections having an arcuate, and in thisexample on an approximately circular arc, outer edge 110 and an arcuate,and in this instance on an approximately circular arc, inner edge 111.Interior edge 111 has a radius at a center of curvature common with thecenter of curvature of housing 50's radiused outer surface so that whenvisual indicator 100 clips to housing 50, the indicator's inner surfacesits approximately flush against housing 50's exterior surface. Visualindicator 100 further comprises tabs 115 that are an extension of shroud105's profile. Tabs 115, comprised of a flexible polymer, deflectoutward in order to allow visual indicator 100 to clip onto housing 50.Tabs 115 wrap around housing 50 greater than 180 degrees and have aradial distance to the center of inner edge 111 (when not attached tohousing 50) that is less than the radius of housing 50's outer surface,so that tabs 115 bias inward and against housing 50, thereby enablingvisual indicator 100 to hold to housing 50's exterior surface. Further,friction between shroud 105 and the outer surface of housing 50 preventsvertical sliding or rotation of shroud 105 along housing 50. In thisway, visual indicator 100 is removably coupled to housing 50 so that itmay be removed without breaking or damaging component parts or breakinga permanent adhesive and thus may be easily removed for repair orreplacement. Alternatively, a very-high-bond double-sided adhesive tapeor other adhesive may be used to hold visual indicator 100 to preventvertical sliding or rotation around housing 50. Further benefits ofvisual indicator 100's clip on attachment include avoiding clamps thatwould otherwise obstruct visual indicator 100's viewing angle or requirea higher profile.

Shroud 105 comprises two vertical through-channels 121 to minimizepolymer volume, thereby reducing material costs and preventing crackingor other deformation from temperature changes during its manufacture anda third vertical through-channel 120 through which a printed circuitboard (PCB) 130 extends. Extruded ridges 129 hold PCB 130 in a generallyfixed location in all directions perpendicular to shroud 105'selongation direction. Extruded ridges 129 prevent PCB 130 from moving ina direction perpendicular to shroud 105's elongation direction withinthrough-channel 120. A close fit between PCB 130 and channel 120 holdsPCB 130 in a fixed location in shroud 105's elongation direction. In afurther embodiment, a silicone gel is placed between PCB 130 and innerwalls of channel 120, which further serves to fix PCB 130's location andprotects the PCB from shock and vibration. Top and bottom caps (notshown) attach via an adhesive or solvent bond to the top and bottom,respectively, of shroud 105. An opening through the top cap providesaccess for electrical communication with PCB 130, and an adhesive shrinktubing covers the opening and one or more cables extending therethrough,thereby isolating PCB 130 from exterior elements (e.g., moisture). Aplurality of reed switches 131 (one shown in FIG. 4) are disposed on PCB130, spaced vertically (into the page with respect to the view of FIG.4). Further, a plurality of light emitting diodes (LEDs) 132 (one shownin FIG. 4) are disposed on PCB 130, horizontally offset with respect toshroud 105's cross-sectional (perpendicular to its elongation direction)line of symmetry and disposed sequentially on PCB 120 so that the LEDsare spaced vertically (into the page with respect to the view of FIG. 4)apart. Each LED 132 is in electrical communication with a respectivelycorresponding reed switch 131 so that PCB 130 has an equal number ofreed switches 131 and LEDs 132 and so that each reed switch is coupledto one respective LED at approximately the same vertical location as thereed switch. Each LED has an intrinsic 180 degree viewing angle. Invarious embodiments, LEDs 132 may be single, dual, or multi-colored,wherein the LED's color may indicate various messages or conditions. Ina still further embodiment, each reed switch electrically communicateswith multiple LEDs.

Because the LEDs have an intrinsic 180 degree viewing angle, absent theshroud, the LEDs are viewable in front of each LED's plane of emissionin all directions within 2*pi steradians. The shape and materialproperties of shroud 105 enable visibility of visual indicator 100 alonga wide solid angle that is greater than 2*pi steradians. Moreparticularly, shroud 105 enables viewing of the LEDs for a viewing anglegreater than 180 degrees, where the viewing angle is bisected by thecenter light-emission axis of each LED and rotated about that axis tothereby define the LED's viewing angle or area. In further embodiments,the viewing angle is greater than 190 degrees. In yet furtherembodiments, the viewing angle is greater than 260 degrees, and in stillfurther embodiments, the viewing angle is greater than 270 degrees. Whena ray of light reaches an interface between two materials havingdifferent indices of refraction, except for light incident at anglesgreater than the interface's angle of total internal reflection, aportion of light is reflected, while the rest of the light is refracted(i.e. transmitted but bent with respect to an axis normal to theinterface at the point of incidence). In the illustrated embodiment, thepolymer shroud 105 has an index of refraction that is greater than thatof air. Thus, for light traveling within the polymer, at each interfacewith the air, a portion of the light emitted from the LEDs passesthrough the interface and into the air, while another portion of lightis reflected back into the polymer. Ray 140 illustrates one path oflight that enables visual indication beyond the intrinsic viewing angleof the LED (which, as should be understood, is a function of the LED'smanufacture). In having a rounded profile (corresponding with outer edge110), shroud 105 provides curved surface and, therefore, a continuum ofreflection angles that concentrate reflection behind the LEDs'forward-facing plane of emission (i.e. for an LED oriented so that theLED's center light emission axis extends horizontally forward from theLED, a vertical plane, perpendicular to the axis and passing through thebase of the LED). That is, the curved surface effectively acts as acurved mirror to concentrate light emitted from the LEDs behind therespective plane of emission for each LED, thereby increasing thebrightness at certain focal points behind the LEDs' respective planes ofemission. Further, the surface of shroud 105's outside face is notperfectly smooth. Thus, a portion of the light passing through itscatters in various directions. Therefore, light hitting the outsidesurface of shroud 105 is viewable from all unobstructed points in frontof a series of planes tangential to the surface at each point at whichlight hits the surface. Because shroud 105's surface is cylindricallycurved, some of the tangential planes will be disposed at a non-90°angle with respect to the LEDs' center light-emission axes (assuming anembodiment in which the LEDs are all aligned with respect to each otherso that their light-emission axes are parallel to each other and in acommon plane). In this way, light from the LEDs will be radiated fromthe shroud, and visible from unobstructed viewing positions, behind theemission planes of the LEDs. Further still, the curved surface does nothave vertically-oriented edges associated with a rectangular profilethat may obscure a direct line of sight to the LEDs. The shape of shroud105, therefore, provides a visual indication over a continuous viewingangle that is greater than 180 degrees with respect to an axis parallelto the elongation direction of the elongated housing. In someembodiments, the viewing angle is greater than 190 degrees, and infurther embodiments, the viewing angle is up to or greater than 270degrees.

Referring also to FIG. 7, reference geometry is disclosed from a toppartial perspective view of the liquid level indicator. Axis 215 extendsinto the page and illustrates a path along which float 80 travels.Since, in this embodiment, housing 50 is cylindrical, axis 215 islocated at the center axis of the cylindrical housing. A first plane 205is tangential to housing 50 opposite tank 10 with respect to axis 215and parallel to axis 215. A second plane 210 is perpendicular to plane205 and encompasses axis 215. Axis 220 is defined by the intersectionbetween plane 205 and plane 210. In some embodiments, visual indicator100 will be visible from all unobstructed positions in front of shroud105 (upward from shroud 105, in the view of FIG. 7) within an areadefined by the sweep of an angle 230 about axis 220 and bisected byplane 210. Due to the configuration of shroud 105 and the disposition ofLEDs 132 within the shroud, light radiated from the LEDs through theshroud is radiated into the viewing area defined by angle 230. Asindicated above, in certain embodiments, angle 230 is greater than 180degrees or greater than 190 degrees, and in further embodiments, angle230 may be up to or greater than 270 degrees. As also indicated in FIG.7, light from the plurality of vertically aligned LEDs 132 (one of whichis visible in FIG. 7) is visible from all unobstructed positions infront of shroud 105 (upward from shroud 105, in the view of FIG. 7)within an area defined by the sweep of an angle about an axis 217 at theintersection of plane 210 and the outer surface of shroud 105 that isbisected by plane 210. Again due to the configuration of shroud 105 andthe disposition of LEDs 132 within the shroud, light radiated from theLEDs through the shroud is radiated into the viewing area defined bythis angle. In certain embodiments, this angle is greater than 180degrees or greater than 190 degrees, and in further embodiments, thisangle may be up to or greater than 270 degrees or 300 degrees.

Ray 225 illustrates a path of light from LEDs 132 that is viewable viareflection by shroud 105 that passes through plane 205; ray 226illustrates a path of light that is refracted by shroud 105 that travelsaway from plane 205; and ray 227 illustrates a path of light that passesthrough plane 205 via scattering at shroud 105's outer surface. Asindicated in FIG. 7, light emitted by LEDs 132 and radiated throughcover shroud 105 is radiated into an area that extends on both sides ofplane 205 and that extends on both sides of a vertical plane 219 that isparallel to plane 205 and includes axis 217 (i.e. is tangential to theouter surface of shroud 105 at axis 217). It should be understood thatwhile LEDs 132 are illustrated as being aligned vertically in the shroudalong a common axis, that this is for purposes of example only, and thatthe LEDs may be disposed in different positions and orientations withinthe shroud. For example, the LEDs may be disposed alternatingly onopposite sides of plane 210.

Reed switches 131 are normally open, and each is configured with amagnetic member that moves under a magnetic field to close the switchand electrically connect a terminal on each side of the switch. Thus,when the magnet within float 80 (FIG. 1) is proximate to a reed switch,the reed switch closes, connecting a portion of a circuit. In theillustrated embodiment, when the switch closes, a circuit through arespective LED 132 is completed, and LED 132 illuminates, as furtherdisclosed below. FIG. 5 illustrates an orientation of reed switches 131on PCB 130 consistent with the present embodiment. Reed switches 131 areoriented vertically with respect to each other, in that a vertical axispasses through a center of each reed switch 131 so that the reedswitches are aligned vertically with respect to each other. The centerof each reed switch aligned vertically on an axis, and each reed switch131 is spaced one-half inch from each adjacent reed switch's center. Inthe illustrated embodiment, the magnet having a predetermined fieldstrength is selected in conjunction with the reed switches' sensitivityand a distance in the horizontal direction between the axis along whichthe magnet within the float travels and the axis upon which the reedswitches are centered so that at any given location along the float'spath, no fewer than one reed switch and no greater than two reedswitches are closed. In the case where two reed switches aresimultaneously closed, the two closed reed switches are adjacent to eachother. In the illustrated embodiment, each reed switch 131 is sensitiveto a magnet at a height within three-eighths of an inch of the height ofthe center of the reed switch. In order to optimize visual indicator100's resolution, reed switches are attached to PCB 130 so that eachreed switch 131's axis is parallel to PCB 130's surface but at an acuteangle with respect to the vertical. In this way, while the length ofeach reed switch 131 is greater than one-half inch, the centers of eachreed switch 131 are vertically spaced within one-half inch of theadjacent reed switches' centers. In further embodiments, the reed switchspacing may vary.

FIG. 6 illustrates a simplified circuit diagram consistent withembodiments of the present disclosure. An 18 mA current source C passesinto a plurality of reed switches. Each reed switch is in series with adiode so that if the reed switch closes, the diode receives current andis illuminated. Further, each reed switch is electrically spaced fromadjacent reed switches by a series of resistors R1 through Rn. In thisway, an output signal may be generated that varies based on the reedswitch that is closed. For example, if reed switch S0 is the only closedswitch, the voltage V2 into the op amp is the cumulative voltage dropacross each resistor R1 through Rn before entering the op amp; if reedswitch S3 is the only closed reed switch, the voltage applied to the opamp is the cumulative voltage drop across each resistor R4 through Rn.Thus, the voltage V2 into the op amp varies by which reed switch orswitches are closed. Further, the current divide between path P1 and P2varies depending on which reed switch or switches are closed. In thisway, the op amp, acting as a differential amplifier, outputs a differentvoltage depending on which reed switch or switches are closed. By addinga gain and offset to the output, the output voltage is scaled from0-10V. The voltage output from the op amp then passes through a signalconverter to provide a 4-20 mA output, wherein 4 mA corresponds to S0being the only closed switch and 20 mA corresponds to Sn being the onlyclosed switch, or vice versa. Generally, the output changes linearly aseach consecutive reed switch is closed. However, slight fluctuations inlinearity may occur when two reed switches are simultaneously closed. AZener diode is in series with a fault LED (e.g., a blue LED) so thatwhen no switches are closed, the voltage across the Zener diodeovercomes the Zener diode's critical reverse voltage, therebyilluminating the fault LED and indicating a lack of a detectablemagnetic field within housing 50. An additional hanging resistor willprovide a signal in excess of 20 mA. In yet further embodiments, a pairof upper and lower LEDs are included in the circuit that are not inseries with reed switches (i.e. always illuminated) and disposed at thetop and the bottom, respectively, of PCB 130, thereby providing anindication of a relative position of the visual indicator's upper andlower limits. That is, the top and bottom LEDs are always lit and not inseries with reed switches to provide reference points for the upper andlower extremes of the visual indicator.

Referring again to FIG. 2, a junction box 180 mounts proximate to thevisual indicator 100. Junction box 180 provides a location forconnecting wires for providing power to PCB 130 (FIG. 4) from a powersource (not shown) for powering the op amp, LEDs, and other circuitry,and providing the current source. Further, as stated above, visualindicator 100 outputs a 4-20 mA signal depending on which reed switch orswitches 131 are closed. For example, the output signal may be 4 mA whenthe lowest reed switch is closed and incrementally increases linearly to20 mA when the highest reed switch is closed. Thus, the output signalindicates how full the tank is along visual indicator 100. In variousother configurations, the output signal may be configured to provide avarying voltage or resistance depending on the float height. The outputsignal is provided to junction box 180 via cable 181, which may connectwithin junction box 180 to a cable that terminates at, for example, amonitor, controller, or process valve. In this way, in addition toproviding a visual LED indication, visual indicator 180 provides anelectrical signal indicating the fluid level in the tank. Wire 181terminates at a plug (not shown) that clips to a receiving portion onPCB 130, thereby enabling easy coupling and decoupling. In furtherembodiments, the controller may provide an alarm when the fluid levelreaches a high or low level set point.

Various features may be included in visual indicator 100. For example, afault LED or audible alarm may indicate the absence of a magnetic field,which may be activated, for example, if the float is damaged or removedfrom housing 50.

The disclosed embodiments provide various improvements over the priorart. For example, conventional flag/magnet indicators can be seen onlystraight on and close up, and cannot be seen in the dark. The disclosedembodiments can be seen in the dark and from a distance. Further, byproviding a wide-angle visual indication, the disclosed embodimentsprovide users with tank level indication from a greater number ofvantage points. Thus, the disclosed visual indicator provides users withtank level information in situations where viewing the fluid levelindicator from certain angles is difficult, for example, in tightlypacked rooms. Users may, therefore, more easily, quickly, andefficiently determine the level of the liquid. In certain situations,the user may respond to the indicated liquid level by, for example,turning on or shutting off pumps.

While one or more preferred embodiments of the invention are describedabove, it should be appreciated by those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope and spirit thereof. For example, Halleffect sensors may be substituted for the reed switches. As anotherexample, in a further embodiment, the tank may have two liquids betweenwhich the float is suspended. In yet further embodiments, the visualindicator may be used with non-liquid fluids. Further, while certaingeometries are shown, various other geometries are consistent withembodiments of the present disclosure. Additionally, many exemplarymaterials are presented, yet various substitutions can be made. Forinstance, many sheet metal parts may be replaced with machined parts.Moreover, while the disclosure uses the term “tank” to refer to a vesselholding a liquid, it should be understood that the term “tank” shouldinclude all vessels capable of holding a fluid.

Accordingly, it should be understood that the elements of one embodimentmay be combined with another embodiment to create a still furtherembodiment. It is intended that the present invention cover suchmodifications and variations as come within the scope and spirit of thepresent disclosure, the appended claims, and their equivalents.

What is claimed is:
 1. A tank and liquid level indicator comprising: a first housing enclosing a first volume that holds a liquid; a second elongated housing enclosing a second volume, wherein the second housing is attached to an exterior of the first housing so that the second volume is in fluid communication with the first volume so that a level of the liquid within the second volume is approximately equal to a level of the liquid in the first volume; a float disposed within the second volume and being buoyant with respect to the liquid so that the float moves with the level of the liquid in the second volume along a first axis passing through a center of the float, wherein at least a portion of the float is magnetic so that a magnetic field extends from the float; a plurality of magnetic sensors aligned sequentially with respect to each other in a direction having a vertical component, wherein the magnetic sensors are disposed with respect to the second volume so that movement of the float within the second volume in response to the level of the liquid within the second volume causes sequential detection of the magnetic field by respective said magnetic sensors of the plurality of sensors; at least one light source in electrical communication with the plurality of magnetic sensors so that the magnetic sensors control actuation of the at least one light source in response to the detection of the magnetic field; and a light-transmissive cover attached to the second housing so that the at least one light source is disposed between the second housing and an outer surface of the light-transmissive cover, wherein the outer surface is disposed on at least one side of a first plane that is parallel to the first axis and at an outer surface of the second housing and is disposed on an opposite side of the first axis from the first housing, wherein the at least one light source is disposed with respect to the outer surface of the cover so that a first portion of light from the at least one light source passes through the first plane and second portion of the light from the light source travels away from the plane.
 2. The tank and liquid level sensor of claim 1, wherein the outer surface extends across and beyond both sides of the plane.
 3. The tank and liquid level indicator of claim 1, wherein the at least one light source comprises a plurality of light sources.
 4. The tank and liquid level indicator of claim 3, wherein each said at least one light source connects to at least one sensor of the plurality of sensors, wherein the at least one sensor is in electrical communication with said light source and a power source so that actuation of the at least one sensor by the magnetic field delivers current from the power source to actuate the at least one light source.
 5. The tank and liquid level indicator of claim 1, wherein the at least one light source is viewable from an angle that is greater than 180 degrees, wherein the angle is defined as an angle swept about a second axis, defined by an intersection between the first plane and a second plane that is perpendicular to the first plane and upon which the first axis lies, and wherein the angle is bisected by the second plane.
 6. The tank and liquid level indicator of claim 5, wherein the angle is greater than 270 degrees.
 7. The tank and liquid level indicator of claim 1, wherein the liquid level indicator further provides an electrical output corresponding with the liquid level, wherein the electrical output is one of a current, a voltage, and a resistance.
 8. The tank and liquid level indicator of claim 1, wherein the indicator is further configured to provide an output signal, wherein the output signal is determined by the detection of the magnetic field.
 9. The tank and liquid level indicator of claim 1, wherein the magnetic sensors have an elongation direction, a center point of sensitivity, and a length, and wherein the magnetic sensors' elongation directions are nonparallel to the second housing's elongation direction and the magnetic sensors are spaced so that the distance between each magnetic sensor's center point of sensitivity and each adjacent′ magnetic sensor's center point of sensitivity is less than each magnetic sensor's length.
 10. The tank and liquid level indicator of claim 1, wherein the magnetic sensors are reed switches.
 11. The tank and liquid level indicator of claim 1, wherein the light-transmissive cover is removably attachable to the second housing.
 12. The tank and liquid level indicator of claim 11, wherein the light-transmissive cover attaches to the second housing via a clip.
 13. The tank and liquid level indicator of claim 12, wherein the clip is a portion of the light-transmissive cover.
 14. The tank and liquid level indicator of claim 1, wherein the magnetic sensors each have a center of sensitivity, and each magnetic sensor's center of sensitivity is spaced by no more than one-half inch from the adjacent magnetic sensors' centers of sensitivity in the second housing's elongation direction.
 15. The tank and liquid level indicator of claim 1, wherein the at least one light source comprises a plurality of LEDs, wherein at least one LED is in electrical communication with each magnetic sensor.
 16. The tank and liquid level indicator of claim 15, wherein a portion of light from the plurality of LEDs is reflected and another portion of the light from the plurality of LEDs transmitted.
 17. The tank and liquid level indicator of claim 15, wherein reflection within the light-transmissive cover causes the plurality of LEDs to be viewable from the angle greater than 180 degrees.
 18. The tank and liquid level indicator of claim 1, wherein the magnetic sensors are spaced with respect to each other and spaced from the float so that a condition is true, wherein the condition is selected from the group of: one magnetic sensor detecting the magnetic field and two adjacent magnetic sensors detecting the magnetic field.
 19. The tank and liquid level indicator of claim 1, wherein the float comprises a magnet selectively spaced in the vertical direction with respect to the bottom of the float so that the magnet is at the liquid level when the float is floating on the liquid.
 20. The tank and liquid level indicator of claim 18, wherein the float comprises a plurality of vertically-spaced slots for receiving the magnet.
 21. A tank and liquid level indicator comprising: a first housing enclosing a first volume that holds a liquid; a second generally cylindrical housing having annular cross-sections and enclosing a second volume, wherein the second housing is attached to an exterior of the first housing so that the second volume is in fluid communication with the first volume so that a level of the liquid within the second volume is approximately equal to a level of the liquid in the first volume; a generally cylindrical float disposed within the second volume and being buoyant with respect to the liquid so that the float moves with the level of the liquid in the second volume along a first axis passing through a center of the float, wherein at least a portion of the float is magnetic so that a magnetic field extends from the float; a plurality of magnetic sensors aligned sequentially with respect to each other in a direction having a vertical component, wherein the magnetic sensors are disposed with respect to the second volume so that movement of the float within the second volume in response to the level of the liquid within the second volume causes sequential detection of the magnetic field by respective said magnetic sensors of the plurality of sensors; at least one light source in electrical communication with the plurality of magnetic sensors so that the magnetic sensors control actuation of the at least one light source in response to the detection of the magnetic field; and a light-transmissive cover attached to the second housing so that the at least one light source is disposed between the second housing and an outer surface of the light-transmissive cover, wherein the outer surface extends across and beyond both sides of a first plane that is parallel to the axis and tangential to an outer surface of the second housing, and the at least one light source is disposed on an opposite side of the first axis from the first housing, wherein the at least one light source is disposed with respect to the outer surface of the cover so that light from the at least one light source passes through the first plane and away from the first plane. 